ok, after reading all the tech articles tying to do my homemade ram/cold air induction system i am confused on what injection type engine is in my car, TPI; TBI or whatever, its a '91 3.1L V6, i'm sure its simple but i've read so many damn tech articles my brain hurts, thnx anybody who clears this up for me.

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91 Blue RS with ASCD SS hood w/hood pins, Flowmaster 80 series w/3 inch dual exhaust, K&N, Hypertech Power Chip, Bosch Platinum wires and plugs.(19 years old and all this bought and paid for by myself, even the car, sorry but i cant stand all those rich little kids who have their mommy and daddy buy all their stuff)

 

Unless I'm mistaken you essentially have the same engine as my 3.1 MPFI (Multi-Port Fuel Injection) in my 92 Bird. Again, I'm unsure, but i believe that the MPFI is a form of TPI. Hope this helps, and if I'm wrong (I have been wrong twice in my life), I'm sorry.

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92 Bird 3.1L Auto
Best $750 I ever spent....

DRIVE IT LIKE YOU STOLE IT!

Kills:
93 Mustang LX (Before Mods)
AIM name OVRCLCK350

 

other way around. TPI is a form of port fuel injection. and yes your engine is MPFI.



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Dan
1990 3.1L RS
80 Series Flowmaster
It's fast(er than a 3 cyl metro)

 

Hey Cali, I am really really wanting to know WHAT IS THE DIFFERENCE between the MPFI ant the TPI? Everyone I've talked to doesn't know. Of course, all of them are clueless to most stuff anyways. Kinda sad evertime I get something for my car, I have to go find my ONE friend that knows anything about cars to tell. Everyone else is like "uh..yah...what's that do?"

 

So it IS TPI? Because i was reading the tech article for the homemade ram/cold air intake system for the TPI and it tells how to set it up for a TPI with two air boxes which i dont have, i have the one cylindrical shaped air box on the passenger side right behind the headlight, does anybody know if they have a tech article for modding it from that

 

To my knowledge and according to my schematics there is very little to no difference.. Chevy just called the V8 version Tuned Port Injection... According to my electrical diagrams even TPI was a bank-fire system until '90, just like the V6 MPFI systems. TPI systems do use a higher fuel pressure, though.. *shrug* could be because of the extra pair of injectors. Don't quote me, and I expect to be shot down by an expert =P

 

not much. i've heard that it's called "tuned" because each intake runner is individually "tuned" to maximize performance. but as far as fuel delivery is concerned, they are identical. each system has an injector for each cylinder located in the intake manifold.(although early TPI motors had 9 injectors). basically, TPI is just a fancy name GM came up with.

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Dan
1990 3.1L RS
80 Series Flowmaster
It's fast(er than a 3 cyl metro)

 

i just converted mine to the 2 air box setup. i tried the ram-air just like in the article but it partially blocked my radiator and caused the engine to run warmer even on the freeway so i scrapped the ram air.



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Dan
1990 3.1L RS
80 Series Flowmaster
It's fast(er than a 3 cyl metro)

 

thats a good idea cali, i would have never thought of converting it to the dual airboxes, thnx.

 

Ok, a little on TPI...

TPI is indeed called Tuned Port Injection because of it's tuned-length intake runners. Don't ask me what the hell a tuned-length intake runner is, but what its supposed to do is by giving each runner its own, unique length, GM was able to maximize torque, at a sacrifice in all-out HP. This shows when comparing the torque and not HP #s of a 350 TPI versus an LS1...the best 350 TPIs of '91-'92 put out 345 lbs/ft of torque (350 in the '90-'91 Vettes), while LS1s put out 325 in the F bodies. Plus, the TPIs max torque is achvieved at a much lower RPM!!!

Why would GM do that?? When TPI was developed in the early '80s, it was thought the V8 was living on borrowed time. This was because of gas mileage and emissions constraints. GM wanted to develop a lower-revving, yet powerful engine for the Fbodies and the Corvette, and found that with then-available technology, TPI gave the maximum grunt for the best gas mileage possible.

A little history lesson


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Jason E
'89 Camaro RS 2.8
Hypertech chip/K&N filters/Accel 8.8 wires,coil/RapidFires
Eclipse CD and 100x4 amp/Boston plates and 6x9s
JasonEE98 on AOL IM

 

They also fire the injectors differently. I believe MPFI fires the left and right bank individually; while TPI fires everything at once. Or is that vice-versa? It's been a while.

mAjInRS, what you're seeing as regards different air intake systems is a result of GM converting from one method of measuring air flow to another. 85-89 2.8's used a MAF sensor, which measures incoming airflow directly. The expensive sensor was a little fragile, so GM went to a "Speed Density" technique of measuring incoming airflow. This is indirectly measured by the vacuum present with the motor. The computer on a SD system has lookup tables that check things such as vacuum, engine rpm, temp, etc- and gives it a # for incoming air flow.

The MAF system is more accurate; the SD system is more reliable. The MAF system responds to heavier mods well; the SD system requires a new chip (since heavy mods go past the limits of the lookup tables).

Your sideways airbox is the result of the SD conversion. The good news is that the dual-snorkel intake of the MAF-equipped Camaros will bolt in... and if you can find it, go for it.

In case you're wondering, Firebirds didn't get the dual snorkel for any year. The clearance between the inside front of the hood and the car frame was too close; so all 85-92 v6/v8 mpfi/tpi Firebirds got a sideways air box.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

he's human after all!!! j/k.... MPFI and TPI both operate all injectors simultaneously. they fire 1/2 the required amount of fuel for every crank revolution.


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Dan
1990 3.1L RS
80 Series Flowmaster
It's fast(er than a 3 cyl metro)

 

TomP, so since i have a hypertech chip, if i build ram/cold air induction system will the chip compensate for what the stock one couldnt? cause if not i guess it could wait till spring time when its a little warmer

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91 Blue RS with ASCD SS hood w/hood pins, Flowmaster 80 series w/3 inch dual exhaust, K&N, Hypertech Power Chip, Bosch Platinum wires and plugs.(19 years old and all this bought and paid for by myself, even the car, sorry but i cant stand all those rich little kids who have their mommy and daddy buy all their stuff)

 

calicamaros,
i heard once that Tuned Port fired the injectors all at once, and Multi Port would fire them when each individual cylinder needed it? that's what i was told, many moons ago.

 

Oh definately, dude. The mods I was talking about are hardcore ones- like an "extreme" camshaft, or head porting jobs, or higher-compression pistons, etc. That stuff's not commonly done with any engine... that's why the TPI V8 guys with SD systems aren't always out there burning new chips. The chip can handle things for quite a while... hope that cleared things up!

Basically as long as you don't do anything wild with the motor (twin-turbos or superchargers included), you'll be fine.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Ok, according to my electrical diagrams, TPI and MPFI both use the same firing solution for the injectors.. there is a difference, but it's between engine types/years, not engine size.
Early MPFI/TPI used a bank fire system.. I can't tell you exactly how much was shot at a time, but it fired one side all at once. In 1990 with the change to the 3.1, dropping mass airflow, and many other changes, MPFI/TPI was changed to fire injectors individually.
This is, once again, according to my diagrams.

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'86 Camaro SC, black /w silver stripes
MSD Coil, Accel 8mm wires, splitfire plugs.. need a job to get this list longer